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Index > Main > Intel has added a new instruction (RDRAND) Kewl !

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typedef



Joined: 25 Jul 2010
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typedef
Say hello to a new instruction RDRAND, Random number generator.

Here is the full changes post: http://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developers-manual.html?wapkw=developers%20manual
Page 9

PS: Requires flash.
Post 17 Aug 2011, 04:50
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DJ Mauretto



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DJ Mauretto
Thanks for your report, Do you know which set of processors support this instruction Question

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Post 17 Aug 2011, 07:16
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AsmGuru62



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AsmGuru62
In that same manual there is a CPUID bit described as indicating the instruction presence.
Post 17 Aug 2011, 13:03
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MazeGen



Joined: 06 Oct 2003
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MazeGen
There's a chapter somewhere at the beginning of the manual that lists processors covered by the manual. Therefore, if the manual introduces new instruction, the most recent processor mentioned in the list should be the first one that supports it. There may be exceptions to this rule, of course.
Post 17 Aug 2011, 16:18
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DOS386



Joined: 08 Dec 2006
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DOS386
> Intel has added a new instruction Kewl !

COOL Smile What does the new KEWL instruction do ?

> PS: Requires flash.

I see ... or not ... I can't download anything from them. Intel brings hot compatibility breaking technology again Sad
Post 18 Aug 2011, 04:39
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Overflowz



Joined: 03 Sep 2010
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Overflowz
DOS386
http://www.urbandictionary.com/define.php?term=kewl Laughing I know, you're just trolling ^^
Post 18 Aug 2011, 09:43
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Tyler



Joined: 19 Nov 2009
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Tyler
Crap, now my processor requires Flash? WTF!
Post 20 Aug 2011, 05:30
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me239



Joined: 06 Jan 2011
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me239
So how do we use? FASM doesn't support it yet, so what's the opcode for it along with the parameters?
Post 20 Aug 2011, 05:58
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revolution
When all else fails, read the source


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revolution
Direct link to PDF:

http://www.intel.com/content/dam/doc/manual/64-ia-32-architectures-software-developers-manual.pdf
me239 wrote:
So how do we use? FASM doesn't support it yet, so what's the opcode for it along with the parameters?
It is explained in the doc.
Post 20 Aug 2011, 06:32
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Tomasz Grysztar
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Tomasz Grysztar
me239 wrote:
FASM doesn't support it yet (...)

Not true. It is supported since 1.69.15
Post 20 Aug 2011, 07:46
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DJ Mauretto



Joined: 14 Mar 2007
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DJ Mauretto
version 1.69.15 (Aug 24, 2010)

[+] Added support for AVX, AES, PCLMULQDQ, FMA, RDRAND, FSGSBASE, F16C, FMA4
and XOP instruction sets. Wink

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Post 20 Aug 2011, 08:10
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DOS386



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DOS386
Quote:
version 1.69.15 (Aug 24, 2010)

[+] Added support for AVX, AES, PCLMULQDQ, FMA, RDRAND, FSGSBASE, F16C, FMA4, KEWL and XOP instruction sets.


1 year ago ... this was HOT news Shocked

> Page 9

NO. Page 11.

> so what's the opcode for it along with the parameters?

$0F, $C7, $F0 (latter for AX / EAX as operand)

Sad it hadn't been in since 8086 Sad

Anyone has an idea how much power or how many transistors it costs ?


Description: KEWL/RDRAND
Filesize: 21.4 KB
Viewed: 15726 Time(s)

KEWL.PNG



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Post 20 Aug 2011, 08:12
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vid
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vid
I wonder what do they use for Nondeterministic random bit generator. Anyone has an idea?
Post 20 Aug 2011, 08:29
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DOS386



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DOS386
Radioactive decay ??? Oops, it produces heat, Alpha or Beta + Gamma radiation, besides nondeterministic behavior Sad
Post 20 Aug 2011, 08:36
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AsmGuru62



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AsmGuru62
I once was a part of a project (1989, I believe) where RNG was done using the delays of a simple OR,AND elements. The fact is that delays between two pulses are not the exactly same - they differ in a miniscule sense, however some are smaller than average and some are larger. It may depend on a number of factors: background radiation levels, sun exposure, cosmic rays, temperature, magnetism, etc. So, basically, very presice pulse generator counts the size of delays and random sequence may be generated. Also, inside the device - the flow of delays can change - it may go through a different set of elements every time a number is generated. I wrote a self-test routine for this to detect if device is working properly.
Post 20 Aug 2011, 12:24
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revolution
When all else fails, read the source


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revolution
Usually the thermal noise across a resistor is the easiest way to generate non-determinism. It is also an easy circuit to make both in the nanometre silicon and the discrete domains. The only real problem with it is the proper way to ensure you don't sample too fast and start getting poor quality bits. Intel seemed to have solved this with a PRNG following the RNG to create higher bandwidth number generation.
Post 20 Aug 2011, 12:28
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emc



Joined: 20 Aug 2011
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emc
I liked the use of RDTSC instruction to get randomized values... Sad
Post 21 Aug 2011, 02:19
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revolution
When all else fails, read the source


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revolution
emc wrote:
I liked the use of RDTSC instruction to get randomized values...
Yeah, and it worked also. But only if your read timings were already random. And only if you throw away the top bits and only use the low few bits. And only if a virus has not put you in hypervisor mode and is manipulating the counter value. Plus, doing that many times in a small loop is generally not a good way to generate high quality randomness.


Last edited by revolution on 21 Aug 2011, 13:23; edited 1 time in total
Post 21 Aug 2011, 12:20
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f0dder



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f0dder
emc wrote:
I liked the use of RDTSC instruction to get randomized values... Sad
I hope you haven't been dealing with cryptography.

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Post 21 Aug 2011, 13:17
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emc



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emc
Don't worry, I haven't been dealing with cryptography (fortunately). But before that new instruction, programmers had to work with rdtsc only?
Post 21 Aug 2011, 14:25
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